There are numerous situations in biological research, ex vivo cell therapies and gene therapies of experimental animals and, eventually, humans, where careful control of the distribution and expression of an introduced gene or a replicating virus is critically important. Viral and non-viral vectors provide means for delivering genes to cells, tissues and organs. However, this delivery is, typically, not specific for any particular cell type, tissue or organ location. Previously, so-called tissue-specific promoters were used to restrict virus replication or expression of a gene delivered by a vector to cells of a specific type. A shortcoming of this approach is that is uncertain whether a “tissue-specific” promoter really exists. Although a promoter may have a much stronger activity in a particular cell type than in others, it is likely to display at least some activity in some other cells. Furthermore, the rate of transcription supported by a chosen tissue-specific promoter, which rate is an intrinsic property of the promoter, may limit its usefulness. Other approaches for controlling expression of therapeutic genes included the use of two-component gene switches that are activated or inactivated by a small-molecule regulator. Well-known switches are controlled by tetracycline, ecdysterone, mifepristone or rapamycin. While these switches may allow for stringent on-off regulation of gene activity, basal gene activity cannot be controlled, and intermediate levels of gene activity are typically difficult to achieve. More important, gene expression cannot be locally restricted by a small molecule regulator that readily diffuses through tissues. Because an activating heat treatment can be directed to a target tissue, heat shock gene promoters should provide an effective means for restricting expression of a gene delivered by a viral or other vector to a target tissue. These promoters have also been suggested to be useful for controlling viral replication (U.S. Ser. No. 09/850270). Some of these promoters, in particular a human hsp70B gene promoter isolated and characterized by the inventor, have minimal basal activity and a heat-induced activity that can be a thousand fold greater than basal activity. Such promoters should be particularly useful for achieving strict regulation of localized gene expression or virus replication. However, there is a downside to using promoters that are activated by transient heat and other proteotoxic stresses. After introduction into an experimental animal or a human, inadvertent activation of these promoters can occur during a fever or ischemia/reperfusion, exercise, exposure to oxidant or other proteotoxic agent, or, possibly, even hormonal stress. The confounding effects of such inadvertent, non-directed activation of virus replication or gene expression will be unacceptable in many applications. Gene switches that are only activated by a combination of heat (or other proteotoxic stress) and a small molecule regulator were previously described and were suggested to be useful for achieving safe spatial as well as temporal control of therapeutic gene expression (U.S. Pat. No. 6,342,596; U.S. patent application Ser. No. 10/046,420).